1. Field of the Invention
The present invention relates to printing hammer assemblies for high speed line printers which utilize a fast moving steel character band and high speed hammer assemblies for hitting the band at the location of the appropriate characters on the band to print upon the band and especially to a low cost striker assembly for actuating the hammer and having an externally adjustable back stop.
2. Description of the Prior Art
The present invention is related to and constitutes an improvement on the high speed printer hammer assembly disclosed in U.S. Pat. No. 4,121,518 to Prior, et al and assigned to the assignee of the instant application. The aforementioned patent is hereby incorporated by reference into this application.
In the impact printing field, a wide variety of printing techniques have been used in the past including those employed in the common typewriter; drum printer; the wheel printer; and the chain or belt printer. In the present type of printer, an endless steel character band having various characters of the alphabet, as well as numbers embossed upon the band, is rotated between a drive pulley and an idler pulley. As the band is driven at high speeds adjacent a platen, a bank of parallel hammers is driven at a high speed at the moment the particular desired character is passing on the band to print the character upon the paper. The print hammer actuators are typically electromagnetically actuated, which magnets are energized by the driving circuit for each pass of the character band. The hammer assemblies need to be spaced close to each other so that a large bank of hammers can fire as the band is passing; and each hammer must respond rapidly in view of the fast moving band which might otherwise smear the character if the hammer is operating at too slow a speed.
An element of such printing hammer assemblies is a striker assembly which comprises the electromagnetic actuating device and a striker utilized to drive the printing hammer. Of key importance to the speed of operation and registration of the printed letters is the exact at-rest position and the operated position of the striker. It is necessary to provide a backstop against which the striker armature rests in the non-operate position and in operation of a high speed printer, on occasions, the backstop must be adjusted to maintain correct operation thereof. Due to the large number of printing hammer assemblies in the banks of assemblies, it has been necessary in the past to partially disassemble this section of the line printer in order to readjust the backstop of a striker armature. Accordingly, the present invention is directed toward a novel and low cost striker assembly having a unique backstop adjustment which may be adjusted externally from the assembly without any disassembly whatsoever.
The above referenced patent application cites a number of U.S. Patents teaching various types of printer hammer assemblies. Additionally, the following also disclose other variations of high speed printing hammer assemblies: U.S. Pat. Nos. 3,968,744 to Kasu, et al.; 3,964,384 to Johnston; and 3,605,611 to Konkel, et al. These prior art patents show adjustment means for the home position of the striker or print hammer; however, none appear to allow accurate adjustment without partial disassembly of their mechanisms.